1. Field of the Invention
The present invention relates to an apparatus for controlling vehicle vibration that sets a predetermined target control value relating to the travel of the vehicle, and controls the vehicle based on the target control value, and also relates to a method of reducing the over-spring vibration of the vehicle.
2. Description of the Related Art
Conventionally, vehicle control apparatuses for reducing the vibration of vehicles are known that control at least one of the engine and the brake in response to an input instruction that is a physical quantity corresponding to at least one of the accelerator operation, steering-wheel operation, and brake operation performed by the driver (e.g., Patent Document 1). Such vehicle control apparatuses correct an input instruction given by a driver in order to suppress vehicle vibration by use of a motion model relating to the vibration resulting from the user input instruction, such vibration including at least one of the up-and-down and/or twisting vibration caused by a reaction force applied to the tires, the under-spring vibration of the vehicle body at the suspension, and the over-spring vibration of the vehicle body that is applied to the vehicle body itself.
[Patent Document 1] Japanese Patent Application Publication No. 2004-168148
In recent years, the needs to stabilize the behavior of a vehicle and to avoid a collision have been recognized in order to improve safety at the time of vehicle travel. To this end, a market progress has been being made with respect to vehicle control apparatuses that set a target control value irrespective of the driver's intension based on the measurement of states and conditions of vehicle travel, and controls the vehicle by arbitrating between the target control value and a target control value responsive to the driver's request. Even in a vehicle that is equipped with such vehicle control apparatus, it is preferable to perform the vibration suppression and correction process as previously described. Since such vibration suppression and correction process results in a change in the dynamic characteristics of the vehicle, the vibration of the vehicle may be increased to destabilize the behavior of the vehicle if the target control value set differently from the driver's request is corrected for vibration suppression, or the vibration-suppressed-and-corrected target control value and the differently-set target control value are arbitrated. When the mechanism for vibration suppression and correction is to be incorporated into a vehicle control apparatus, however, it is not desirable, from the viewpoint of cost and burden associated with the development, to design the vehicle control apparatus in conformity to the vibration-suppression-and-correction mechanism.
Accordingly, there is a need for a vehicle control apparatus and vehicle vibration-suppression method that can suppress vehicle vibration satisfactorily, and can easily and properly ensure the safety of the vehicle when a target control value is set in response to conditions different from the driver's request.